Guest Cowdood Posted June 22, 2006 Share Posted June 22, 2006 I'm new here to this forum and also to Z cars but I'm learning. I've got a '78 280Z that's not running in the best of shape. When I'm driving and I'm accelerating at a slow-to-moderate pace the engine (atleast, I think it in the engine) hesitates at about 2k RPMs. Once in the this hesitation, I can't get passed it unless I give it a consideral amount of gas and it jumps over that spot. It runs fine in all other RPMs except for when I'm accelerating and I hit about 2k RPMs and it stutters. I'm guessing it could a vacuum problem somewhere because there is an open hose connection on the throttle catch, but that might not be the problem. Thank you guys so much for a great Z car info site! http://forums.hybridz.org/showthread.php?t=79940&highlight=engine+hesitates+2k+rpms My problem is similar to this guy's problem but it's not exactly the same (which is why I posted a new thread). This guy says something about not having the air filter on, which is a coincidence because there is no air filter on this car either. Could that be it? Thanks again Adam Quote Link to comment Share on other sites More sharing options...
Twizted Posted June 22, 2006 Share Posted June 22, 2006 Actually it sounds like the throttle position sensor. Although there are many things it could be but I'd start there. Quote Link to comment Share on other sites More sharing options...
olie05 Posted June 22, 2006 Share Posted June 22, 2006 yes, tps would be the first. then I would check the connection on the water temp sensor by the thermostat housing. And after that check the operation of the afm. It could be sticking. have you gotten yourself a copy of the EFI BIBLE? Quote Link to comment Share on other sites More sharing options...
Guest Cowdood Posted June 22, 2006 Share Posted June 22, 2006 have you gotten yourself a copy of the EFI BIBLE? Not that I know of... I do have the original 1978 280Z Owner's Manual. Does the manual refer to this mechanism as the "throttle position sensor" or does it call it something else? Quote Link to comment Share on other sites More sharing options...
Cruez Posted June 22, 2006 Share Posted June 22, 2006 Owners manual won't have squat about the inner workings of the Z Only general maintenace. Quote Link to comment Share on other sites More sharing options...
Guest Cowdood Posted June 22, 2006 Share Posted June 22, 2006 Owners manual won't have squat about the inner workings of the Z Only general maintenace. It's the huge, 2 inch book that has everything about the car in it. Has everything from how to check the oil, to completely disassembling and then re-assembling the engine. It's the original repair manual, I guess I should have said. Sorry. Quote Link to comment Share on other sites More sharing options...
mentallylost Posted June 22, 2006 Share Posted June 22, 2006 http://www.freewebs.com/crookedduck/280zfuelinjectionbook.pdf It's a larger file so it takes a bit to download. But it's the 280z Fuel Injection Book. aka EFI Bible. Quote Link to comment Share on other sites More sharing options...
Z-TARD Posted June 23, 2006 Share Posted June 23, 2006 Thanks for the link, Mentallylost. I'm having similar issues with my own 280Z and this should help quite a bit. Mike Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted June 23, 2006 Share Posted June 23, 2006 I'm going to second (third?) the guess for throttle position sensor. Specifically that the two sets of points inside are both making a connection at the same time. If you pop off the cover on the throttle position sensor you will see two little sets of contact points. one set makes connection when the throttle is completly closed. This indicates to the ecu that the throttle is closed. The second set makes contact (or should) when the throttle is open a large amount (like three quarters open or more) This indicates to the ecu that the throttle is open big time and causes an enrichment for full power. A guy who was a nissan tech back when the 280 was a current model showed me how to adjust it. It was the first thing he said when I told him my fuel injection wasn't working. You adjust it by (gently) bending the contact point arm. He told me it was real common for them to end up both touching at once and that was bad. Work the throttle as you adjust, make the first set touch just before the throttle is completly closed. Make the second set touch when you get the throttle almost fully open, allow some travel in the middle where neither touch and make sure they don't touch at the same time. In my experience, when the coolant temp sender goes bad, the system just goes full rich. (indicated by much black smoke & running for crap, barely able to idle) I am preparing a SCCA ITS 280, so by the rules I must use the stock fuel injection with all the stock sensors. This has caused me to spend some time learning about this system. It's crude, but the more I play with it, the more impressed with it I am. I'd like to learn more. So... sorry for the long post, Ztard what's wrong with your's? oh and sorry, the FI bible is a must have. It explains basic theory then all the service procedures. The factory service manual has it all as well. Quote Link to comment Share on other sites More sharing options...
Z-TARD Posted June 23, 2006 Share Posted June 23, 2006 Mine seems to be running really rich. It smokes quite a bit and the idle is really rough. For about the first ten minutes or so after starting it up it runs well enough to drive, but it seems that once it warms up something goes really wrong. Any attempt at acceleration stalls out the motor, this happens without any noticable smoke, so I'm thinking that it leans out too much after it warms up. It also fouls out plugs like nobodys business, probably due to the rich mixture when cold. I'm going to print out a copy of the 280 FI book and take it with me to Tuscon next time I go out there to work on it. Hopefully I can figure this out and get it running well enough to pass smog out there. Mike Quote Link to comment Share on other sites More sharing options...
Guest Cowdood Posted June 24, 2006 Share Posted June 24, 2006 Is the "throttle position sensor" the same thing as the "throttle valve switch?" I'm using my book trying to locate it. Thank you guys so much for the help. I want to fix this myself, instead of someone else charging me huge money to fix it. Plus I just want to learn more about cars! Thanks again Adam *Edited* I just figured out the answer to my question after reading the EFI book. Thanks for the book. I'll see if this will fix my problem. Once again thank you guys. Quote Link to comment Share on other sites More sharing options...
MIBPreacher Posted June 24, 2006 Share Posted June 24, 2006 That is an expensive part new at 50+ dollars, i paid 16 for mine used. You have to play with it unless you have the meter to measure it. Good luck. Quote Link to comment Share on other sites More sharing options...
Twizted Posted June 24, 2006 Share Posted June 24, 2006 Z-Tard yours sounds like the Cylinder temp sensor. Those are very common to cause problems. Check the resistence at different temps and compare them to the specs in the manuel. AFM could also be the culprit tho, but I'd start with the temp sensor. I also go thru plugs more than tanks of gas. It's because I'm screwing with the natural settings of the comp and having it run rich for when I "get on it". I bet yours runs great at open throttle, right? Quote Link to comment Share on other sites More sharing options...
Z-TARD Posted June 24, 2006 Share Posted June 24, 2006 Z-Tard yours sounds like the Cylinder temp sensor. Those are very common to cause problems. Check the resistence at different temps and compare them to the specs in the manuel. AFM could also be the culprit tho, but I'd start with the temp sensor. I also go thru plugs more than tanks of gas. It's because I'm screwing with the natural settings of the comp and having it run rich for when I "get on it". I bet yours runs great at open throttle, right? Yeah, open throttle is a white knuckle ride, only to be followed by lots of stuttering and hesitation when you let off. I have a brand new temp sensor as well as two junkyard AFM's that look to be in decent condition. Also got a rebuilt 280ZX distributor to swap into it as well since the vac. advance plate in mine was shot. Hopefully these parts should get it running right again, I'd like to get this thing out of my brothers yard and out here to San Diego so I can finally have a running Z again. Mike Quote Link to comment Share on other sites More sharing options...
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